This invention relates to fuel cells, for example solid oxide fuel cells. More particularly, this invention relates to methods for manufacturing fuel cells. This invention also relates to fuel cells manufactured by such methods.
Solid oxide fuel cells (SOFC""s) in part comprise a solid electrolyte layer interposed between two electrodes, the electrodes comprising an anode and a cathode. The electrolyte layer is usually dense so as to be impermeable to gas flow and comprises a material that is an electron insulator and an ion conductor, such as, for example, stabilized zirconia. The electrolyte layer is also generally desired to be as thin as possible to minimize resistance to ionic conduction within the electrolyte layer. In contrast to the dense electrolyte, both the anode and the cathode comprise pores to allow flow of gas within each electrode in order to maintain a local environment suitable for the electrochemical reactions taking place therein. The cathode usually comprises a ceramic material that is doped for high electrical conductivity, such as strontium-doped lanthanum manganite (also referred to herein as lanthanum strontium manganite), and is maintained in an oxidizing atmosphere, such as air or other gas comprising oxygen. The anode usually comprises a mixture of a metal with a ceramic, such as nickel with stabilized zirconia, and is maintained in a reducing atmosphere, such as a gas comprising hydrogen. Interconnection plates, also referred to herein as xe2x80x9cinterconnects,xe2x80x9d often electrically connect several anode-electrolyte-cathode units (hereinafter referred to as xe2x80x9cfuel cell unitsxe2x80x9d) with one another to form a fuel cell assembly.
SOFC electrodes and electrolyte layers are typically manufactured using conventional ceramic fabrication methods, such as tape casting, coat-mix processes, and screen printing. Such methods are limited in their abilities to manufacture desirably thin layers, because they often generate undesirable defects, such as voids and inclusions, within the manufactured layers, increasing the fragility of the inherently brittle ceramic materials; furthermore, these methods involve a significant amount of physical manipulation of the fragile layers, which increases the risk of damaging the article during the manufacturing process. Finally, these methods require significant amounts of time to manufacture and assemble the fragile layers in a fuel cell assembly.
An increasing demand for fuel cells having higher power density drives a need for thinner electrodes and electrolytes, and thus there is a need to provide improved methods for manufacturing thin, mechanically robust fuel cell components and assemblies. Furthermore, there is a need for improved methods that reduce the manufacturing and assembly time of fuel cell components. Additionally, there is a still further need for fuel cell components and assemblies that are thin and sufficiently robust to withstand the rigors of manufacturing, assembly, and operating stresses.
Embodiments of the present invention are provided to address these and other needs. One embodiment is a method for manufacturing a fuel cell assembly, comprising providing at least one fuel cell unit. Providing the at least one fuel cell unit comprises providing at least one substrate and disposing at least one fuel cell component layer on the at least one substrate, the at least one component layer comprising at least one of an interconnect, an anode, a cathode, and an electrolyte. Disposing the at least one component layer comprises depositing the at least one component layer using an expanding-thermal-plasma coating (ETP) apparatus.
A second embodiment is a fuel cell assembly manufactured by the method of the present invention.